title: Diels-Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton.
abstract: Regioselective construction of 4,8,9-trioxygenated 2,3-dihydrobenz[f]indenones, key intermediates for the synthesis of kinamycin antibiotics, was achieved via Diels-Alder reactions (DAR) using 4,7-dioxygenated indanone-type compounds as dienophiles. Reaction of indanetrione with 1-methoxybutadiene gave a 1 : 1 mixture of undesired 4,5,9-trioxygenated 2,3-dihydrobenz[f]indenone and [4.4.3]propellane. The addition of Lewis acid did not affect the product ratio, whereas the use of the 6-bromoindanetrione exclusively afforded the latter propellane. On the other hand, DAR of benzyne derived from bromoindan and furan gave 5,8-epoxy-2,3-dihydrobenz[f]indene, which was subjected to acid-induced ring opening to give 2,3-dihydrobenz[f]indenone with undesired 4,5,9-trioxy functions.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho Inage-ku, Chiba 263-8522 Japan.
authors.forename: Natsuno
authors.initials: N
authors.lastname: Etomi
authors.forename: Takuya
authors.initials: T
authors.lastname: Kumamoto
authors.forename: Waka
authors.initials: W
authors.lastname: Nakanishi
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Ishikawa